Man, that hits home. My own grandma's place had that same slow-cooker smell, onions softening for hours in her stew. You could tell she'd been standing there a long time, just stirring and waiting. It wasn't about fancy food, it was about making sure we all felt fed and cared for. That smell is a memory of being loved, plain and simple.
Hold up, onions and patience? My grandma's kitchen smelled like onions and burnt butter half the time. She was not a patient woman. She just had a cheap stove that took forever to boil water. Maybe the patience was us waiting for it to be edible.